In a semiconductor manufacturing process, defects including particles, scratches, etc. in a semiconductor substrate (wafer) surface cause failures including insulation failures, short circuit, etc. of wires formed on the wafer and cause insulation failure of capacitors and breakdown of gate oxide films. Accordingly, it is important to detect defects in the wafer surface in the semiconductor manufacturing process and feed back the defects to the semiconductor manufacturing process.
For the detection of defects, the so-called surface inspection apparatus is used. An example of the surface inspection apparatus includes an optical inspection apparatus that detects defects on a substrate by irradiating the substrate with examination light and detecting the scattered light. The optical inspection apparatuses may be roughly classified into surface inspection apparatuses that examine mirror wafers (bare wafers) and patterned wafer surface inspection apparatuses that examine wafers on which circuit patterns have been formed. In the specification, both inspection apparatuses are referred to as “surface inspection apparatuses” and their inspections are referred to as “surface inspections”.
In a manufacturing process of a semiconductor device, a step of creating a resist pattern by transferring a pattern to a resist coating a wafer surface, a step of etching using the created resist pattern as a mask, and a step of removing unnecessary parts on the wafer surface are executed. Accordingly, particles, scratches, etc. attached to the wafer surface are a major factor for decline of yield.
On this account, in the respective manufacturing steps, the above described surface inspection apparatus is used for detection and management of particles attached to the wafer surface, defects existing on the wafer surface, etc. with high sensitivity and high throughput. Further, in the surface examination, wafer surface roughness has not only an influence on the performance of the photolithography process but also a significant influence on the detection sensitivity.
Accordingly, measurement of the wafer surface roughness is highly required.